The international criminal court is issuing summonses for six Kenyans – including the deputy prime minister and the president's closest aide – who stand accused of crimes against humanity related to the violence that followed the disputed 2007 election.

The summonses were sought by ICC prosecutor Luis Moreno-Ocampo in December. His naming of the six suspects sent shockwaves through the government, and has prompted a desperate effort by President Mwai Kibaki's camp to discredit the court and have proceedings deferred.

The ICC case relates to the bloodshed that followed the 2007 presidential election, which Kibaki is widely believed to have rigged to stay in power. More than 1,300 people were killed by police or in ethnic attacks, which human rights groups say were planned and financed by leading politicians. The coalition government failed to set up a local tribunal to punish the main perpetrators, as it had promised to do when a peace deal to end the bloodshed was signed, prompting the ICC to step in.

The Ocampo Six, as the Kenyan media have dubbed them, will have to appear in The Hague on 7 April. The first case involves Uhuru Kenyatta, the deputy prime minister, finance minister and son of the country's founding president Jomo Kenyatta; cabinet secretary Francis Muthaura, regarded as Kibaki's gatekeeper; and the former police chief Hussein Ali. While some of Moreno-Ocampo's evidence was rejected as insufficient, the judges ruled that there were reasonable grounds to believe that Kenyatta and Muthaura were "criminally responsible as indirect co-perpetrators" for murder, rape, forcible transfer of population and other inhumane acts. The alleged crimes all relate to revenge attacks by Kikuyu gangs on civilians from other ethic groups. Evidence suggested Ali could be "criminally responsible as having contributed to [the same] crimes", the judges ruled.

The second case relates to the initial round of ethnic violence by Kalenjin militias in Rift Valley province. It involves William Ruto and Henry Kosgey, who both cabinet ministers under suspension over fraud claims, as well as radio presenter Joshua Arap Sang. The three judges ruled by majority decision that there were grounds to believe Ruto and Kosgey were responsible as indirect co-perpetrators of murder, forcible transfer of population and persecutions. It was reasonable to believe that Sang "contributed to crimes" of a similar nature, the court said.

The court's decision may spell the end of Kibaki's efforts to have the case deferred. This week he dispatched envoys to lobby all UN Security Council members for a 12-month stay on the ICC proceedings, on the grounds that Kenya needs time to establish a special local tribunal to deal with post-election crimes. But most local commentators have interpreted the move as a ploy to save his allies from facing international justice.